* {
    padding: 0;
    margin: 0;
}

body,
html {
    width: 100%;
    height: 100%;
    background-color:black;

}

.blood {
    width: 200px;
    height: 30px;
    background-color:transparent;
    border: 3px solid #ccc;
    position: relative;
}

.blood .num {
    height: 30px;
    background-color: red;
    position: absolute;
}